1. Field of the Invention
This invention relates to an image projecting apparatus for enabling an image recorded on a microfilm to be projected on a magnified scale on a screen and more particularly to an image projecting apparatus furnished with an image rotating mechanism for enabling the image in process of projection onto the screen to be rotated to a desired posture.
2. Description of the Related Art
In the operation of an image projecting apparatus such as a reader for enabling an image recorded on a microfilm to be projected on a magnified scale on a screen or a reader printer for copying a projected image, there are times when the image on the microfilm needs to be projected on the screen with the posture thereof suitably rotated instead of being projected directly in its original posture on the screen. The reason for this necessary change of posture is that all the images are not photographed in a prescribed posture in a microfilm; some of the images are photographed as slightly tilted or, in the case of a microfiche having a multiplicity of image frames recorded thereon after the fashion of a matrix, some image frames are recorded as arranged longitudinally and others as arranged laterally, so that the posture of image frames varies depending on the kind of film.
The image projecting apparatus, therefore, is designed to be provided in a projected light path with an optical image rotating mechanism formed of a Dove prism, so that no matter what posture an image frame may assume on a film, the image projected from this frame will be projected in a desired posture on the screen. An operator of the image projecting apparatus which is furnished in the projected light path with the image rotating mechanism as described above moves the image frames on the film sequentially past the projector orifice or makes fine adjustment of their positions relative to the projector orifice while keeping an eye on the images projected on the screen for the purpose of retrieving a desired image frame from among the multiplicity of image frames recorded as arrayed after the fashion of a matrix on a microfiche, for example. At times, the direction in which the film is actually moved fails to conform with the direction in which the series of image frames is moved past the screen. When the operator, in an effort to take a look at the left side of the image currently projected on the screen, moves the film unwittingly to the right by manipulating a key bearing a leftward arrow mark on the control board, the image may possibly be moved in completely the opposite direction, depending on the angle of rotation of the prism used in the microfiche. If this apparatus allows of an accident of this nature, it is deficient in operational efficiency. The operating panel or the control board is provided with keys bearing arrow marks indicating the four directions, i.e. the upper, lower, left, and right directions. In the conventional apparatus, these arrow-marked keys correspond only to the directions of movement of the film. Since the directions of movement of the image on the screen do not agree with the directions of the arrow marks indicated on the keys, the operator is at a loss for selection of a right key on a given occasion.
Japanese Patent Application Laid-Open 63-235,922 discloses an image projecting apparatus adapted so that the direction in which the film should be actually moved correctly is displayed on a display part, depending on the condition of rotation of an image rotating mechanism. In the case of this apparatus, the operator is required to manipulate the movement of the film while comparing the direction in which the image is desired to be moved on the screen with the direction in which the film is to be actually moved.